People who accidentally go over their smartphone plan's data limit know that they need to scale back their app use. But finding out which apps are hogging the data can be tricky. A new database run by CTIA-The Wireless Association called Know My App hopes to point users in the right direction, revealing how the most popular apps for both iOS and Android consume data.

Jackie McCarthy, the director of wireless Internet development at CTIA, said that the database was created to better inform smartphone users about their app habits. "While things like voice minutes and text messages are pretty intuitive, data usage isn't as intuitive for many consumers to understand," she told ABC News. "There was nothing out there that allowed consumers to go out and look at how the most popular apps treat data before they're installed."

Know My App isn't a personalized report tailored to each smartphone's data habits, but more like ballpark estimates. Intertek, an independent app testing company that assisted CTIA in creating the database, calculated each app's data usage by assuming how the typical smartphone owner uses each app in a day.

For example, it assumed that in one day, YouTube users watch one minute of video three times a day, among other tasks such as marking what videos to watch later or subscribing to new channels. Those short YouTube clips add up to over 3 GB of data in a single month.

Brett Parsons, program manager at Intertek, said that it's not surprising to see YouTube and Netflix as the apps with the highest data usage. "All video applications use a lot of data," he said. "But there have been a lot of surprises. You can see apps that are simple games but are also using gigabytes of data."

Currently, Know My App only has a handful of the most popular apps. "To start with, we're just testing the top 50 free and paid apps in both Apple's and Google's store each month," said McCarthy. Parsons added that Intertek will continue testing apps at least for the next two years and that the database will be regularly updated.

For anyone looking to personally reign in their data usage, one of the easiest things that Parsons suggests it to use your phone's Wi-Fi option, including on the go. "Most major retailers offer Wi-Fi, so that's definitely a way to go," he said. "If you're in an area that has Wi-Fi and want to stream video, that's kind of an obvious way to do it."

But for the power user that wants to know exactly how all their apps are using data, Parsons recommends the same tools that Intertek uses for testing. "There's a tool that AT&T developed called Application Resource Optimizer, or ARO," he said, which is available for free download on the AT&T developer website. "You can do a lot of analysis, including how these apps affect a phone's battery life."